The future arrival of the ubiquitous computing age brings about the needs to input information seamlessly to information equipment in a variety of locations and scenes and to operate the information. In particular, devices that input and output positional information, movement, and pointing information of an object or personal in arbitrary spaces are very important in constructing a user interface that is easy to use.
Conventionally, for-example, operations by contact with an interface portion, or extremely close proximity to the interface portion, have been developed as pen input and finger input on a display device or on a projection screen of a projector. An infrared pen input device has been proposed (refer to Japanese Patent Application Laid-Open No. H08-249112). In such device light from an infrared light emitting device of an external frame member of a screen is reflected by use of a stylus pen, and the position of the pen can be identified by a light-receiving device based on a visual angle of the reflected light. In this case, it is not necessary for structural members to be on the screen, and there are advantages in that the screen can be made in a large size, and there is no interference with a display device.
On the other hand, although remote controls have been in use for a long time for operations at distant locations, there are limitations to the operating functions thereof, and it is difficult to acquire highly accurate positional information. On-vehicle radars (refer to Japanese Patent Application Laid-Open No. H09-318737), for example, are used in detecting positions in space. The distance to an object can be measured with such radars by using laser light or electromagnetic pulses of millimeter waves or the like, based on a time difference until detecting reflected waves from the object.
There is a problem, however, with the infrared light pen input device described above in that detection becomes impossible if the light is blocked, and further, operations on a surface of the screen are basically necessary. Furthermore, since the method using a laser radar or millimeter wave radar allows distance measurements in a free space, vehicles and large size devices used outside have been developed. However, small size, lightweight devices used for a user interface have not been considered. In particular, something that is less interfered by obstacles than light and uses an electromagnetic wave method using millimeter waves or the like is necessary for a remote input/output interface system under a ubiquitous computing environment.